2012 AMC 10B Problems/Problem 13
Solution
Let be the speed of the escalator and
be the speed of Clea. Using
, the first statement can be translated to the equation
. The second statement can be translated to
. Since the same distance is being covered in each scenario, we can set the two equations equal and solve for
. We find that
. The problem asks for the time it takes her to ride down the escalator when she just stands on it. Since
and
, we have
seconds. Answer choice
is correct.